# I don't really understand the unit circle that well...

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• Sep 28th 2008, 07:39 AM
gobbajeezalus
I don't really understand the unit circle that well...
...and would love some help with various problems. I'll start with some of the simple ones from my homework and if people help me on those, i will ask more (Nod)

Using the unit circle, find each value.

1. sin 90
2. tan 360
3. cot -180

It's so confusing, I don't get it at all. This is how far i got for #1:http://img.skitch.com/20080928-afi99...kweqsc5huw.jpg

Now, I thought that one part of that triangle will equal 1. but what part?

thanks!!!!
• Sep 28th 2008, 07:57 AM
skeeter
any point on the unit circle has coordinates $\displaystyle (x,y) = (\cos{\theta}, \sin{\theta})$

so ... what are the coordinates at the top of the circle where $\displaystyle \theta = 90^{\circ}$ ?
• Sep 28th 2008, 07:58 AM
gobbajeezalus
(0, 1)?
• Sep 28th 2008, 08:31 AM
skeeter
good! so, now you know $\displaystyle \cos(90) = 0$ and $\displaystyle \sin(90) = 1$.